Electronic devices usually comprise electronic elements, such as central processing units (CPUs), which may generate heat when in operation. Heat sinks are usually used in the electronic devices for dissipating the heat generated by the electronic elements. However, structures of heat sinks are usually complicated and are voluminous. The heat sinks may take up a large amount of space of the electronic device. Therefore, the usage of heat sinks in electronic devices may impede the progress of electronic device miniaturization. Improvement in the art is preferred.